Most wills can be executed by families without too much difficulty and when expert help is needed, lawyers can be used, costing just a few hundred pounds.

But High Street giants including Royal Bank of Scotland/NatWest, HSBC, Lloyds TSB and Barclays take as much as 4% of estates valued up to £300,000 - a tidy sum of £12,000 - for acting as executors of a will.

Consumer groups and charities have attacked the high charges. David Sinclair at Help the Aged, says: 'I think these fees are outrageous. There are alternatives and I urge people to shop around the army of solicitors available.'

The role of executor involves registering the death, working out how much the assets are worth, paying any inheritance tax due and distributing the proceeds.

Last week, Money Mail highlighted a case involving HSBC, which charged a staggering £18,000 to prove what seemed to be a very straightforward will.

It charges 4% on the first £300,000 of the value of the estate and then 2% on anything above that. This is on top of a flat fee of £750.

HSBC says: 'We provide a top quality service and 99% of customers say they are satisfied or very satisfied overall. We are also completely transparent about our fees, and it is very important that people ask what fees will be charged.'

NatWest, for instance, charges 4% on the first £250,000 of the value of an estate and 2% above this. However, it says it will make 'big discounts' for simple cases.

The average house price now stands at £201,090 for the country as a whole and £296,160 in London. So for handling a basic estate involving simply selling a house and distributing the money, a bank could charge from £8,044 to £11,846.

If you had been saving into tax-free cash mini Isas since they were launched in 1998, you would have saved £27,000 before interest is added. Distributing this would add another £1,000-plus to the bill.

Lloyds TSB charges a flat rate of 4% regardless of the size of an estate, but says the service is exclusive to its private banking customers. The minimum investable assets to apply for private banking are £250,000, so an estate with a modest house is likely to be at least £500,000 - generating at least £16,000 in fees.

Once again, the bank says it will reduce the costs for 'unusually simple' cases. It is slightly more complicated at Barclays, as it says fees are based not only on the value of your estate but the level of activities it needs to carry out to distribute the monies and the number of assets involved.

In a simple scenario, where an estate is valued at just £80,000 with three assets worth more than £500, then the total fee would be £4,100 - a fee of 5.1%, according to Barclays. In a slightly more complicated and larger estate, a widow leaving £300,000 to a son or daughter would bring costs of £12,800 - a fee of 4.3%.

Barclays says a reduction in fees is possible if the administration 'has proved exceptionally straightforward'. Those not comfortable with the idea of asking family members to execute wills would generally do far better to use a lawyer.

Richard Grosberg, partner at Midlands-based law firm Nelsons, says: 'A solicitor tends to charge based on the amount of work they carry out, but a lot of the tasks can be done yourself if you have the time. A simple probate can cost as little as £250.'